Simplify the following expression: $p = \dfrac{9k}{4} + \dfrac{7k}{5}$
Solution: In order to add expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $4$ and $5$ $\lcm(4, 5) = 20$ $ p = \dfrac{5}{5} \cdot \dfrac{9k}{4} + \dfrac{4}{4} \cdot \dfrac{7k}{5} $ $p = \dfrac{45k}{20} + \dfrac{28k}{20}$ $p = \dfrac{45k +28k}{20}$ $p = \dfrac{73k}{20}$